Monomer of `[NH-overset(O)overset(||)C-NH-CH_(2)]n` is:

Options

A. Methanamine
B. `N` Methyl urea
C. Formaldehyde
D. Ammonia

Answer

To determine the monomer of the polymer represented by the structure `[NH-overset(O)overset(||)C-NH-CH_(2)]n`, we will analyze the structure and identify the components that form the polymer.

### Step-by-step Solution:

1. **Identify the Structure of the Polymer**:
The given polymer structure can be broken down as follows:
- The repeating unit contains a carbonyl group (C=O) attached to two nitrogen atoms (NH).
- There is also a methylene group (CH2) connected to one of the nitrogen atoms.

2. **Recognize the Name of the Polymer**:
The structure resembles that of urea formaldehyde resin. This resin is formed from the polymerization of urea and formaldehyde.

3. **Identify the Monomers**:
- **Urea**: The chemical formula for urea is NH2CONH2 (or simply NH2C(=O)NH2).
- **Formaldehyde**: The chemical formula for formaldehyde is CH2O (or HCHO).

4. **Determine the Monomer for the Given Polymer**:
The polymer `[NH-overset(O)overset(||)C-NH-CH_(2)]n` is derived from the combination of urea and formaldehyde. Therefore, the monomers involved in the formation of this polymer are:
- Urea
- Formaldehyde

5. **Evaluate the Options**:
The options given are:
- Methanamine
- N-methylurea
- Formaldehyde
- Ammonia

Among these, formaldehyde is one of the monomers used in the formation of the urea formaldehyde resin.

6. **Conclusion**:
The correct answer is **formaldehyde** as it is one of the monomers that combine with urea to form the polymer.

### Final Answer:
The monomer of the polymer `[NH-overset(O)overset(||)C-NH-CH_(2)]n` is **formaldehyde**.